In modern wireless networks, such as an LTE- or LTE-A mobile-radio network, the right to transmit, for example, payload data via the control channels in a flexible manner is communicated to a mobile-radio device, so that the bandwidth available in a mobile-radio cell can be used efficiently by many mobile-radio devices with an optimum bandwidth. When a mobile-radio device requests a data connection, a code is allocated to it by a transmitter device within the mobile-radio network. Control messages for this mobile-radio device are then marked with the allocated code and transmitted on a transport channel together with control messages for other mobile-radio devices which are disposed in the same radio cell.
In order to find its own control messages, the mobile device implements so-called blind decodings. Accordingly, the mobile-radio device searches through a so-called “search space” (“search space”) of the transport channel, for example, as described in the 3GPP standard TS 36.213, and establishes via a check-value comparison (CRC check), whether the control message is intended for this mobile-radio device. In the LTE specification 3GPP TS 36.212, a check-value length of 16 bits is used, and up to 40 blind decodings per second are implemented.
In order to minimize the number of these blind decodings and to design them as effectively as possible, U.S. 2011/0116428 A1 describes blind decodings of control channels which result in several valid check-values, so that different mobile-radio codes are checked. As a result of the large number of check-value calculations, the number of error detections rises significantly, that is to say, control channels are accepted although they are not intended for the decoding mobile-radio device. This leads to an error transmission of data and accordingly to a deterioration in the transmission quality. In order to reduce the number of error decodings, the control channels are checked with regard to further criteria, such as the number and structure of filler bits. The control channel is accepted only if these are met.
A further source of error detections results from the fact that control channels are transmitted even when no information needs to be transmitted to the mobile-radio device. In this context, the control channel is defined with noise or a random bit sequence. Accordingly, a randomly correct check-value for the random bit sequence can occur with a statistical probability of 2-check-value length. For example, in the case of a check-value (CRC) length of 16 bits and up to 40 blind decodings per millisecond, 0.6 error detections per hour occur. This also means that the mobile-radio device incorrectly interprets the control channel as an authorization to transmit data and therefore contributes to a disturbance of the channel.
In addition to a general increase in the noise level, such error detections are disturbing in conformity tests. For example, a mobile-radio device is tested for spurious emissions (spurious emissions) in this manner. Error detections in a mobile-radio device and a subsequent transmission of data by the mobile-radio device falsify or disturb such a test procedure.
What is needed, therefore, is an approach for reducing or preventing the number of error detections in a simple manner generating minimal operational loading, for example, in a mobile radio device or a base station in a mobile-radio network.